Change heuristic to determine which fields contain modifieable double boxes: do it if field was ini…

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
diff --git a/runtime/vm/parser.cc b/runtime/vm/parser.cc
index d5f5ca30c09ecea8c50f0b56a13fd3f366162c85..b02bf40f3eb24fcac0edbc90eb1170472694546b 100644
--- a/runtime/vm/parser.cc
+++ b/runtime/vm/parser.cc
@@ -3972,7 +3972,8 @@ void Parser::ParseFieldDefinition(ClassDesc* members, MemberDesc* field) {
       // value is not assignable (assuming checked mode and disregarding actual
       // mode), the field value is reset and a kImplicitStaticFinalGetter is
       // created at finalization time.
-      if (LookaheadToken(1) == Token::kSEMICOLON) {
+      if ((LookaheadToken(1) == Token::kSEMICOLON) ||
+          (LookaheadToken(1) == Token::kCOMMA)) {
         has_simple_literal = IsSimpleLiteral(*field->type, &init_value);
       }
       SkipExpr();
@@ -4008,6 +4009,9 @@ void Parser::ParseFieldDefinition(ClassDesc* members, MemberDesc* field) {
     // and rules out many fields from being unnecessary unboxing candidates.
     if (!field->has_static && has_initializer && has_simple_literal) {
       class_field.RecordStore(init_value);
+      if (!init_value.IsNull() && init_value.IsDouble()) {
+        class_field.set_is_double_initialized(true);
+      }
     }
 
     // For static final fields (this includes static const fields), set value to